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H. W. Urbarz 《Astrophysics and Space Science》1996,243(1):203-207
The list of mass ejections published in Solar Geophysical Data during the period of Jan. 1981 to Oct. 1987 contains about 1300 Surges, Sprays and Type II bursts. The relationship between the mass ejection events and the shock front events is investigated by means of correlation of time and position. The result shows that type II bursts start as frequently after the mass ejections as prior to them. 相似文献
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A. Bhatnagar R. M. Jain J. T. Burkepile I. M. Chertok A. Magun H. Urbarz P. Zlobec 《Astrophysics and Space Science》1996,243(1):209-213
The powerful cosmic ray flare of Sept. 29, 1989 occurred behind the limb and was observed over a wide spectral range. The analysis of optical, radio, and other relevant data suggest two phases of energy release. After an impulsive phase a prolonged post eruption energy release occurred in an extended region of the corona following the eruption of a large coronal mass ejection (CME). This phase is responsible for numerous coronal and interplanetary phenomena including the ground-level increase of cosmic rays. 相似文献
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H. W. Urbarz 《Solar physics》1986,104(1):125-129
A total number of 460 DCIM events, single or groups, were observed during the period of October 1980 to December 1984 with the Weissenau spectrograph as dynamic film spectra. Several parameters describing these data were evaluated statistically and the main features were discussed in context with associated burst types.Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985. 相似文献
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Agalakov B. V. Ledenev V. G. Lubyshev B. I. Nefedyev V. P. Yazev S. A. Zubkova G. N. Kerdraon A. Urbarz H. W. 《Solar physics》1997,173(2):305-318
Based on observations from the Siberian solar radio telescope, and invoking data from other observatories, we investigate preflare changes in the sunspot and floccular sources of radio emission and the development of an importance 2N flare in the chromosphere and corona in the active region on August 23, 1988.It has been ascertained that preflare changes became observable six hours prior to the flare onset and manifested themselves in intense flux fluctuations above the sunspot and in an enhancement of the source emission flux above the flocculus.It is shown that the flare onset is associated with a newly emerged magnetic flux in the form of a pore near the filament and with the appearance of radio sources above the filament. The flare was accompanied by type III radio bursts and a noise storm at meter wavelengths. Coronal mass ejection parameters are estimated from type III burst observations. 相似文献
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Bhonsle and Degaonkar (1980) have presented an evidence for the Razin-cutoff frequency in the dkm range of type IV continuum observed by the Ahmedabad spectroscope on 27 April, 1979. They explained this cutoff as due to the Razin effect in the coronal medium. From the broad-band spectrograph at Weissenau, covering 1000 to 30 MHz, additional information on the initial features of type IV is furnished here. This record also confirms the preceeding type II burst, the shock front of which was assumed to produce the quasiperiodicity observed at the lower cut off frequency by interaction with the type IV radiation source. 相似文献
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We studied the properties of fine structures in 23 type II bursts recorded at the Trieste Astronomical Observatory at frequencies above 200 MHz.The lifetime of a single fine structure is a fraction of a second. The ratio of fine structures intensity vs bulk flux density is different in different type II bursts and it changes during the evolution of a single event; the reported maximum ratio is 3. The polarization of fine structures is nearly the same during the lifetime of an event. There is also no essential difference in polarization between fine structures and bulk emission; this holds also for an example of high-polarization (about 80%) event.At frequencies lower than 200 MHz the analogy between herringbone structure and type III bursts is frequently mentioned in the literature. From the observations we studied, it results, however, that the time profile of single fine-structure elements and their polarization are substantially different from the morphology of type III bursts.The observed fine structures and their characteristics are discussed in the framework of the model by Holman and Pesses (1983).Paper presented at the 4th CESRA Workshop in Ouranopolis (Greece) 1991. 相似文献
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It is shown that the existing theory of type II bursts, based on a model of the emission from the shock wave front, has difficulties when compared with observational data. We suggests a new model for type II bursts. According to this model, in an expanding magnetic loop a cluster of energetic electrons acts to excite the cyclotron instability of plasma waves. The waves are excited on surfaces where the cyclotron resonance condition is satisfied, and are then transformed into electromagnetic emission by merging. Our proposed model may be useful to explain some observational facts, such as the narrow-band character of the emission and the space-time relationship between the harmonics. Some tests to check the validity are proposed. 相似文献
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B. Vršnak V. Ruždjak M. Messerotti Z. Mouradian H. Urbarz P. Zlobec 《Solar physics》1987,114(2):289-310
We present observations of the flare of May 14, 1981, which can be classified as a three-ribbon flare. After a detailed analysis in metric, decimetric, microwave, optical, and X-ray ranges we propose that the event was caused by a reconnection process driven by erupting filament. The energy was liberated in the current sheet above the filament in the region between the erupting flux and the overlying field. It is shown that plasma microinstabilities develop as the plasma enters the current sheet. The observations indicate that during the precursor phase a certain low-frequency turbulence, such as ion-accoustic turbulence had to be present.The reconnection rate was growing due to the increasing tension of the stretched overlying field. It is shown that the reconnection proceeded in the Sonnerup-Petschek regime during the precursor, and changed to the pile-up regime in the fast reconnection phase, when the maximal lateral expansion (50 km s–1) of the H ribbons was observed. The proposed process of reconnection driven by an erupting filament can be applied to three- and four-ribbon flares. 相似文献
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